Prosecutor Susan Badger told U.S. District Judge Charles Breyer that additional charges and defendants will be added in the next 90 days.
Some 29 people, including suspended state Sen. Leland Yee, already have been indicted. Yee has pleaded not guilty to bribery and gun charges.
The new charges in the case might contain racketeering charges. However, prosecutors didn't identify who could be charged under the Racketeer Influenced and Corrupt Organizations Act, better known as RICO.
"Of particular note, the government is continuing to pursue its investigation of RICO violations as well as additional substantive criminal violations,'' prosecutors told the judge in a court filing handed to him during a routine hearing.
Racketeering charges carry maximum penalties of 20 years in prison and hefty fines and civil penalties, including seizure of property. Such counts enable prosecutors to charge leaders of gangs with crimes they ordered others to carry out.
Yee and his attorney Jim Lassart declined comment Friday after the hearing in San Francisco federal court. Prosecutors also declined comment.
Experts and many of the two dozen lawyers involved in the case, had expected racketeering charges to be included in the indictment unsealed last week. However, no racketeering charged were filed.
The lawyers and the judge have already agreed that not all the defendants will be tried together because of the myriad different and unrelated charges many face.
Lumping 29 people charged with a combined 50 charges in a single indictment was a "ploy to make the indictment seem stronger than it is,'' said Curtis Briggs, one of three lawyers representing defendant Raymond "Shrimp Boy'' Chow, the leader of a Chinese community organization who is charged with 10 counts of money laundering and receiving stolen goods.
Briggs said Chow plans to plead not guilty when he is arraigned on Tuesday.